Batteries power a wide array of devices, from cell phones to electric or hybrid cars. Circuits to precisely measure battery voltage are required in many applications. Measuring battery voltage, for example, provides a way to determine how much charge remains in the battery and whether the battery should be replaced or recharged.
In many applications, instead of a single battery, battery banks are used that consists of an array of batteries connected in series, in parallel, or a combination of series and parallel. In order to determine how much charge remains in the battery bank, each battery within the bank should be measured. However, some of the batteries within the battery bank may not be referenced to ground if they are connected in series. The positive and negative terminals of these batteries may sometimes be floating at relatively high voltage, i.e. 60-250 V or more above ground. Measuring the voltage across each of these batteries may require expensive circuitry or may consume a large amount of power during measurement.